Highway crossing gate control system



Dec. 8, 1953 J. c. LINDNER HIGHWAY CROSSING GATE CONTROL SYSTEM FiledJune 18, 1949 u @N r I. L I. IL 25M??? 20 DE HEB jun Q2 E5: =0 26:

Ihwentor c. an m Patented Dec. 8, 1953 HIGHWAY CROSSING GATE CONTROLSYSTEM John C. Lindner, Rochester, N. Y., assignor to General RailwaySignal Company,

Rochester,

Application June 18, 1949, Serial No. 100,066

1 Claim. 1

This invention relates to highway crossing protection mechanisms and thecontrol of such mechanisms and more particularly pertains to theelectrical control of gate arms which are lowered over a highway uponthe approach of a train.

Varying conditions are often encountered in the use of gate arms of thistype which greatly affect their operation. Under conditions of sleet andice, for example, a gate arm may be frozen into its clear position sothat it cannot drop by the force of gravity upon the approach of atrain. In addition, a gate arm of this type may also be prevented fromdropping due to the force of high winds. For this reason it isconsidered desirable to drive the gate arm downward during the firstportion of its descent to assure it is not being held in the clearposition.

On the other hand, a heavy load of ice upon the arm or a heavy wind maycause it to descend too rapidly. Or the wind blowing upon the gate armmay be of such a force and direction as to cause the arm to drop moreslowly than it otherwise would. Either condition, 1. e. too fast or tooslow dropping of the arm, is considered detrimental to safety becausefast dropping of the arm may cause it to strike the tops of passingvehicles which have not yet come to a stop; whereas, slow movement ofthe gate arm might permit highway trafiic to cross the railroad trackswhen the train is dangerously close to or actually at, the intersection.For these reasons a stand- 'ard, relatively uniform time of descent isconsidered advantageous in the operation of highway crossing gates.

In prior types of highway crossing gates in which the gate is drivendownward during a portion of its descent, the rate of descent changesappreciably at the end of the drive-down period. Also, many of thesegates are provided with some type of mechanical braking. In the gate armmechanism of the present invention, however, the rate of descent issubstantially constant during its entire travel and, in addition, onlyelectrical braking is used so that less wearing of parts results.

A further object of the present invention is to provide a means ofcontrol for a highway crossing gate which will permit the gate to beraised immediately upon the passage of a train while yet permitting thedescent of the gate to be delayed upon approach of a train so thathighway traific may be warned of the gates impending descent.

Other objects, purposes, and characteristic features of the presentinvention will be in part matically and certain conventionalillustrations have been employed, the drawings having been made morewith the purpose of making it easy to understand the principles and modeof operation, than with the idea of illustrating the specificconstruction and arrangement of parts that would be employed inpractice. Thus, the various relays and their contacts are illustrated ina conventional manner, and symbols are used to indicate connections tothe terminals of batteries, or other sources of electric current,instead of showing all of the wiring connections to these terminals.

Although two crossing gates are commonly employed at a highway crossing,only the control apparatus and circuit for one gate 6 has been shown inthe accompanying drawing. Except for certain of the equipment shown inthe accompanying drawing which is common to both of the gate mechanismsat a typical highway crossing, the remainder of the equipment shown isassociated only with one of the gate mechanisms with similar apparatusordinarily being provided for the other gate. The equipment common toboth of the gates includes the GP relay and its control circuit, theflasher relay and the relays TP and TPP.

Each gate mechanism has associated therewith a rotary contactor, variouscontacts of which are included in the circuit shown in the accompanyingdrawing. These contacts are illustrated diagrammatically by means of arevolving contact and a circular segment with which it makes contact,the revolving contact being operated from the. shaft 1 through thequadrant gears S and 9. In each of these diagrammatic illustrations theposition of the revolving contact corresponds with the position of thegate and is shown in a vertical position when the gate 6 is cleared andin a horizontal position when this gate is lowered over the highway. Thenumerals associated with each contact indicate the angular position ofthe gate arm for which that particular contact is closed. Thus, thecircuit of relay GP is shown as including contact 45 which is closedwhen the gate is in a position between 75 and 90, the zero degreeposition corresponding to the horizontal position of the gate and the 90position corresponding, of course, to the gate arms vertical position.

An interlocking relay IR. is shown in the accompanying drawing and thisrelay is controlled by an associated track circuit in such a manner thateither front contacts In and l l or front contacts l2 and i3 will becomeopen when a train approaches the highway crossing. If, for example, aneastbound train approaches the crossing, the front contacts l2 and I3will be opened and will remain open until the rear of the train haspassed over the crossing. Because of the mechanical interlockingprovided by this relay IR, contacts l and H will not be opened by thepassage of this eastbound train beyond the highway crossing. Similarly,when a westbound train approaches the crossing, front contacts l0 and IIwill be opened. Since the contacts 10 and 12 are included in series tocontrol the relay GP and the contacts H and iii are included in seriesto control the relay TP and relay TPP and since these relays arenormally energized, the effect of the interlocking relay upon theapproach of a train is to cause the deenergization of these relays whenthe train is at some specified distance in approach of the highwaycrossing and to condition the circuits for the reenergization of theserelays when the rear of the train clears the crossing.

Under the normal condition shown in the accompanying drawing, thevarious contacts of the interlocking relay are shown closed so thatrelays GP, TP, and TPP are all picked up. When a train approaches thecrossing, these relays will become deenergized as already described.Since the relay GP is a quick releasing relay, it will immediately dropaway and close its various back contacts. The closing of its backcontacts 14 and I will permit energy to be applied to the various lampsshown in accordance with the position of contact ll of the flasherrelay. The closing of back contact IE will energize this flasher relay,and cause its armature to oscillate so as to intermittently close itsfront and back contacts. When front contact I! of this flasher relay isclosed, the lamps 20 and 2| on the upright highway signal and the lamp22 on the gate arm are energized through a circuit from back contact Mof relay GP, front contact ll of the flasher relay; through the lamps20, 2|, and 22, back contact l5 of relay GP, to Similarly, when the backcontact I! of the flasher relay is closed, the lamps 23, 24 and 25 aresimilarly energized while the lamps 2B, 2 l, and 22 will then bedeenergized. In this manner, the lights on the highway signal and on thegate arm are caused to flash intermittently. The lamp 26 located on thetip of the gate arm is continuously illuminated when back contacts 14and I5 of relay GP are closed. The closing of back contact 21 of therelay GP energizes the bell 28 thereby producing an audible warning toapproaching highway traflic of the approach of a train.

e e ys TP and TPP are both deenergized by the approach of a train as hasbeen described. Although the relay TPP is of the ordinary type in thatit has quick releasing characteristics, the relay TP, on the other hand,is provided with slow releasing characteristics as shown by the heavybase line for the symbol designating this relay. Thus, although therelay TPP will drop away quickly and open its front contact 30 upon theapproach of a train, the relay TP will remain in its picked up positionfor a time interval corresponding to its slow releasing characteristics.Since the contact 30 of relay TPP and the contact 3| of relay TP areincluded in parallel in the circuit controlling the hold clear magnetI-IC, it is evident that even though the front contact 30 is quicklyopened upon the approach of a train, the circuit to the hold clearmagnet I-IC will not be interrupted. As will presently become apparent,the dropping away of the hold clear magnet HC causes the gate arm todrop. Therefore, the afiect of the slow releasing characteristics of therelay T? is to delay the descent of the gate 5 while the various lampsflash and the warning bell rings, thus warning approaching highwaytraffic that the gate is about to drop.

Under the normal condition as shown in the drawing, the hold winding 1-1of the hold clear magnet HC is energized through contacts 39 and 3| ofrelays TPP and TP respectively. Consequently, with front contacts 29 ofthe hold clear magnet HC closed, the motor circuit cannot be energizedsince the contact 32 of the rotary contactor is open when the gate is inits normal, upright position. Also, with the hold clear magnet EC in itsenergized condition, the pawl I8 is moved into position so as to engagethe ratchet wheel 33 on the motor shaft and in this way downwardmovement of the gate is prevented while the gate is in its normalposition even though the motor including armature A and field windingsUF and DF is deenergized.

Upon the release of front contact 3| of relay TP, the hold clear magnetEC is deenergized as has been described. As a result, both back contacts29 and 34 will be closed and the pawl l8 will be released and biased bythe spring 5 so as to disengage the ratchet wheel 33 so as to permitrotation of themotor armature A. A circuit for the motor will then beestablished from back contact 29 of the hold clear magnet HC, contact 35of the rotary contactor, the down field winding DF and the motorarmature A to Also a shunt field circuit will be established for themotor from the point 36, through the up field winding UF, back contact34 of the hold clear magnet HC resistor 31 to Thus, in effect ashort-shunt compound motor connection is provided in which the up fieldseries winding UF for the motor is used as the shunt field. Since thisfield winding UP is of relatively low resistance as compared to anordinary shunt field, the resistor 3'! is included in series with thewinding in order to limit the current through it. As will presently bebrought out, the direction of current flow through the up field windingUF (from left to right in the drawing) is opposite to the direction ofcurrent flow when thi winding U1? is used as a series field to drive thegate to its upward position. For this reason, the shunt field fluxproduced by this winding UP is of such a polarity as to aid the downfield DF in driving the gate to the downward position. As shown in thedrawing the motor armature A drives the gate arm 6 through the speedreducing gear box GB.

As is shown in the diagrammatic view of the gate in the accompanyingdrawing, the gate arm 6 is counterbalanced by a weight at to reduce thedownward turning moment of the arm. In practice, the arm is so balancedas to have its maximum turning moment while in the clear position,reducing to a minimum value as the gate reaches the horizontal position.The reason for this arrangement is that a wind blowing upon the gatearm'will produce the least upward turning torque upon the gate when itis in its horizontal position and also the downward turning torque dueto a heavy load of ice coating the gate is at a maximum when the gate isin its horizontal position. Therefore, although a large downward turningtorque is desirable when the gate is in its clear position, such a largeamount of torque is not required when the gate assumes lower positionsfor the reasons mentioned above and also because of the inertia of thegate as it revolves. The downward turning torque as the gate reaches its45 position is such, however, that it will continue to drop of its ownaccord even when under the influence of various external forces and, forthis reason, ener y is removed from the motor when the gate reaches thisposition as will presently be described. Depending upon the particularconditions encountered, however, the motor may actually function eitheras a generator or as a motor during the drive-down period depending onwhether torque is being applied to the motor shaft or whether torque isbeing expended by the motor shaft upon the gate arm. The speedtorquecharacteristics of a compound machine of this type are such, however,that its speed will remain within a relatively narrow range even thoughthe torque applied to or expanded by the motor should vary.Consequently, the gate will be lowered at a fairly uniform rate evenunder adverse conditions caused by ice, wind, or the like.

Referring again to the drawing, it can be seen that contact 35 of therotary contactor opens when the gate arm is in its 45 position and thatthe contact 48 of the rotary contactor closes when the gate arm is inits 44 position. The opening of the contact 35, of course, removesenergy from the motor armature and from the down field winding DF. Thistermination of the drive-down period, although shown in this particularembodiment as occurring at the 45 position of the gate arm may as welloccur at some other position. The 45 position was here chosen because itcan safely be assumed for reasons already mentioned that at this pointthe gate arm will continue to travel downwardly due to the force ofgravity. In order to prevent a sudden change in the speed of descent ofthe gate arm when the drive-down period is ended, the contact 49 isclosed just after the end of the drive-down period and by doing soconnects the resistor 4! in parallel with the resistor 37. As a result,the total eifective resistance in series with the shunt field winding UFis decreased so that the total shunt field current may then increase.For this reason, the shunt field flux will also increase and thisincrease of flux will compensate for the removal of energy by theopening of contact 35. The proper value of resistance for the resistor4| may most readily be determined by experiment for, with someparticular value of resistance the speed of descent of the gate arm willbe substantially unchanged at the end of the drivedown period.

The gate arm then continues to drop at a relatively uniform rate untilit reaches a position '10 above the horizontal at which time contact 42of the rotary contactor becomes closed. The closing of this contact 42places a short circuit across both resistors 4i and 31. As a result, thebraking action on the motor shaft is greatly increased so that its speedof rotation drops to a low value. ;By this .means, the gate arm isbrought to its horizontal position with a minimum of shock to themechanism. Also, as the gate arm reaches the 3 position, the circuit tothe bell 28 is opened by the opening of contact 44 thereby preventingthe bell from ringing and producing an unnecessary disturbance duringthe time that the gate arm remains in its horizontal position.

When the passing train recedes from the highway crossing and the frontcontacts of the interlocking relay IR which were previously opened bythe approach of the train become closed. a circuit is establishedthrough the front contacts II and I3 of this interlocking relay IR toenergize both relays TP and TPP. As was previously stated, the relay TPis provided with slow releasing characteristics. Although it is desiredthat this relay '1? be of the quick pick-up type, a relay of this typewhich is provided with slow releasing characteristics will also havesomewhat slower pickup characteristics. For this reason, the relay TPPis provided which will quickly pick up upon the passage of the trainthereby allowing the gate arm to be quickly raised so as not to obstructhighway traffic longer than is neces-' sary. Upon the closing of frontcontact 30 of relay TPP a circuit is established to energize the PWinding of the hold clear magnet HC. This hold clear magnet is of thetype which employs two separate windings P and H; one (P) for picking upthe armature and the other (H) for holding it up after it has once beenpicked up. The pick-up winding P of this hold clear magnet HC is of alower resistance than the hold winding H so that a greater current andtherefore more flux will be produced by this pick-up winding than by thehold winding H. The amount of flux thus produced by this winding P issufficient to pick up the armature of the hold clear magnet when it isin its dropped away position. Circuit means, presently to be described,are included for deenergizing the pick-up winding P after it has oncebeen picked up and for allowing the magnet to remain picked up by meansof its higher resistance (lower power consuming) hold winding H.

When the armature of the hold clear magnet HC is picked up, and itsfront contacts 29 and 34 closed, a circuit is established to energizethe motor from contact 32 of the rotary contactor, the up field windingUP, the motor armature A, to It will be noted that in this instance thedirection of current through the up field UF was from right to left andthus opposite to the direction of current flow through this winding whenit was used as a shunt field for driving the gate arm downwardly. Beingthus energized, the motor operates to raise the gate arm to its verticalposition. The picking up of the hold clear magnet HC also causestherpawl I8 again to engage with the ratchet wheel. Be-.

cause of the unsymmetrical shape of the teethof this ratchet wheel 33,however, the motor isrnot restrained fromdriving the gate to its upwardposition.

Examination of the circuit controlling the operation of relay GP showsthat contact of the rotary contactor is open while the gate arm is inits horizontal position. Thus, when the contacts l0 and I 2 are bothclosed immediately following the passage of a train past this highwaycrossing location, the relay GP cannot become energized and, as aresult, the lights on the gate closes and allows the relay GP to becomeenergized. Back contacts I4, 15, and [6 of this relay GP are then openedwith the result that the lights then no longer flash and the bell 28stops ringing. Also, when the gate arm reaches its 75 po- ;sition, thecontact 46 of the rotary contactor opens thereby deenergizing the pickup winding 'P. As has been described, this hold clear magnet HC, when inits picked up position, can be maintained in that position by theenergization of the hold winding 1-1. As the gate arm continues to riseand finally reaches the 88 position, the contact 32 of the rotarycontactor opens thereby deenergizing the motor. The inertia of the gatearm is of course sufficient to carry it to its vertical, 90 positioneven though it is deenergized at the 88 position.

It follows from the foregoing description then that the presentinvention provides an improved means for governing the operation ofhighway crossing gates in that it permits them to descend at arelatively uniform speed even while under the influence of variousexternal forces. Also, this circuit for controlling a crossing gate isso arranged that the gate arm will quickly begin to rise upon thepassage of a train even though it also embodies the provision ofdelaying the descent of the gate upon the approach of a train until theflashing lights and ringing hell have warned approaching trafl'icof thegates impending descent.

Having described a circuit for controlling a gate arm as one specificembodiment of the present invention, it is desired to be understood thatthis form is selected to facilitate in the disclosure of the inventionrather than to limit the number of forms which it may assume; and it isto be further understood that modifications, adaptations, andalterations may be applied to the specific form shown without in anymanner departing from the spirit or scope of the present invention.

What I claim is:

In a control system for a highway crossing gate, a normally energizedhold clear magnet for mechanically latching said gate in an uprightposition, said magnet being deenergized only when a train is in approachto and crossing said highway, a rotary contactor having contacts whoseoperation is governed by the angular position 0! said gate, a motorincluding an armature and two field windings for driving said gate toselected upward and downward positions, circuit means governed by saidhold clear magnet and efiective when said hold clear magnet isdeenergized for energizing One of said field windings in series withsaid armature and for connecting the other 01' said field windings inshunt across said armature, the polarity of energization of saidwindings being chosen in relation to the polarity of current in saidarmature to cause said motor to drive said gate downwardly, said circuitmeans being effective when said hold clear magnet is energized and saidgate is in its downward position to energize said armature in serieswith said other field winding, the polarity of energization of saidother winding being chosen in relation to the polarity of current insaid armature to cause said motor to drive said gate upward.

JOHN C. LINDNER.

References Cited in the file Of this patent UNITED STATES PATENTS NumberName Date 1,818,013 Smith Aug. 11, 1931 2,137,196 Sampson Nov. 15, 193820,154 Howe et al Nov. 5, 1940 2,310,694 Henry Feb. 9, 1M3

